Background Diabetic patients undergoing percutaneous coronary intervention (PCI) have a higher incidence of contrast-induced nephropathy (CIN) than nondiabetic patients, and no pharmacological approach has been demonstrated to offer consistent protection. Therefore, identifying individuals who are at increased risk becomes essential. This study was designed to assess the predictive role of the ratio of contrast medium volume to estimated glomerular filtration rate (CMV/eGFR) in diabetic patients undergoing elective PCI who developed ClN.Methods We retrospectively investigated clinical factors associated with the development of CIN in 114 diabetic patients who had undergone elective PCI. The risk factors for CIN included age, gender, body mass index (BMI), left ventricular ejection fraction (LVEF), hemoglobin (Hb), fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), volume of contrast medium, basic levels of serum creatinine (Scr), the number of treated vessels and the number of stents used.We conducted a stepwise regression analysis to evaluate the predictive role of these risk factors in the incidence of CIN.Results The incidence of CIN was 18.4％ (21/114). There were no significant differences in age, gender, BMI, LVEF, Hb,FPG, HbA1c, and incidence of hypertension and number of acute myocardial infarction (AMI) in patients between the CIN (n=21) and the non-CIN (n=93) groups. However, the eGFR was significantly lower ((72.0±12.5) ml·min-1·1.73 m-2 vs.(82.0±16.5)ml·min-1·1.7m-2, P=0.010), and the basic serum creatinine level ((1.07±0.12) mg/dl vs.(0.97±0.19) mg/dlP=0.014) was significantly higher in the CIN group. In addition, the volume of contrast medium was significantly larger rn((253±75)ml vs. (211±71)ml, P=0.017) and the CMV/eGFR ratio was significantly greater (3.64±1.26 vs.2.70±1.11,rnP=0.001) in the CIN group. Stepwise regression analysis showed that the CMV/eGFR ratio was a significant independent predictor for the development of CIN (P=0.001). At a cut-off point of ＞3.1, the CMV/eGFR ratio exhibited 71％ sensitivity rnand 70％ specificity for detecting CIN.Conclusion The CMV/eGFR ratio could be a valuable predictor of CIN for diabetic patients after elective PCI. At a cut-off point of＞3.1, the CMV/eGFR ratio was an optimal predictor for the incidence of CIN.